The present invention relates generally to the application of energy to biological tissue, and specifically to the application of electromagnetic energy to the skin.
It is known in the art to apply electromagnetic energy to biological tissue to engender changes therein. Sunbathers, for example, regularly expose themselves to bright sunlight in order to increase melanocyte activity in the basal layer of the epidermis, responsive to the sun""s ultraviolet (UV) radiation. Artificial UV sources have been created to satisfy the desire for a xe2x80x9chealthyxe2x80x9d looking tan in the winter. Other forms of electromagnetic energy, laser-light in particular, are currently used in a large range of therapeutic and cosmetic procedures, including eye surgery, hair removal, wrinkle removal, and tattoo removal.
PCT publication WO 98/55035, which is incorporated herein by reference, describes methods for minimizing injury to biological tissue surrounding a site exposed to pulses of electromagnetic energy.
U.S. Pat. No. 5,752,949 to Tankovich et al., which is incorporated herein by reference, describes a hair-removal method for placing a contaminant in the skin, using a laser to create explosions to drive the contaminant deep into hair ducts in the skin, and subsequently heating the contaminant to kill biological tissue surrounding the contaminant. The rate of application of energy is controlled to allow cooling of the skin.
U.S. Pat. No. 5,814,040 to Nelson et al., which is also incorporated herein by reference, describes a method for port wine stain removal, including applying a coolant to the skin, and subsequently directing laser radiation below the cooled area.
U.S. Pat. 5,810,801 to Anderson et al., which is also incorporated herein by reference, describes a method for treating wrinkles in the skin, including directing electromagnetic energy to a target region of the skin, while cooling an area above the target region.
It is an object of some aspects of the present invention to provide improved apparatus and methods for applying energy to a material.
It is another object of some aspects of the present invention to provide improved apparatus and methods for removing heat generated during application of electromagnetic energy to a material.
It is a further object of some aspects of the present invention to provide improved apparatus and methods for removing heat generated during application of electromagnetic energy to biological tissue.
It is still a further object of some aspects of the present invention to provide improved apparatus and methods for decreasing pain during application of electromagnetic energy to biological tissue.
It is yet a further object of some aspects of the present invention to provide improved apparatus and methods for performing medical treatments.
It is also an object of some aspects of the present invention to provide improved apparatus and methods for performing cosmetic treatments.
It is further an object of some aspects of the present invention to provide improved apparatus and methods for enabling a visible wavelength electromagnetic energy source to perform material and tissue removal and modification.
It is yet a further object of some aspects of the present invention to provide methods and apparatus for enabling a visible wavelength low-power electromagnetic energy source to perform material and tissue removal and modification.
It is still a further object of some aspects of the present invention to provide methods and apparatus for enabling a low-power electromagnetic energy source to perform material and tissue removal and modification.
It is also an object of some aspects of the present invention to provide improved methods and apparatus for enabling a low-power electromagnetic energy source to perform tissue removal and modification, substantially without pain, while controlling the amount of damage to remaining tissue.
In preferred embodiments of the present invention, an energy source applies electromagnetic energy to tissue of a subject, preferably so as to ablate a portion thereof. Thereafter, some of the heat generated by the interaction of the energy with the tissue is removed, typically by applying a coolant or a cooling element to the tissue. Removal of the heat immediately following the application of the energy generally reduces the subject""s sensation of the heat, and, in particular, reduces any sensation of pain. Moreover, heat removal typically reduces or eliminates collateral injury to tissue surrounding the ablated area. Typically, although not necessarily, the tissue comprises the subject""s skin.
It is known in the art to cool tissue prior to or during the application of electromagnetic energy to a subject""s skin. U.S. Pat No. 5,814,040 cited above, for example, describes cooling the epidermis prior to heating tissue thereunder, to minimize damage to the cooled tissue. Similarly, U.S. Pat No. 5,810,801 describes cooling a first region of tissue while heating a second region of tissue thermally coupled thereto. These embodiments of the present invention, by contrast, teach that cooling the tissue following the application of electromagnetic energy is generally advantageous. Furthermore, it is believed that very rapid heating of a target area of the skin, substantially unmitigated by any prior cooling thereof, produces therapeutic results that are superior to techniques which cool a mass of tissue and then apply energy to a cooled target area. In particular, it is believed that the prior art methods which describe cooling of an upper tissue layer prior to interaction of electromagnetic energy therewith generally have an adverse effect on modification and/or ablation of tissue in the upper layer. Notably unlike techniques as taught according to preferred embodiments of the present invention, these prior art methods generally are painful in the absence of an administered anesthetic.
In some preferred embodiments of the present invention, the energy source comprises a laser, whose beam is moved in a pattern over a target area of the skin. The pattern is made up of a sequence of passes over the tissue, each pass describing a line or curve over a predetermined portion of the target area. Typically, the pattern is chosen such that each pass is relatively distant from the preceding one, so that it generally does not cause additional heating of tissue indirectly heated by energy from the preceding pass. The temperature of this latter tissue decreases during the succeeding pass, preferably to approximately the same temperature as prior to the preceding pass. In some of these preferred embodiments, the laser energy is applied to the skin in sets of passes, whereby a set of one or more consecutive passes of the laser across the skin is relatively distant from a preceding set of one or more consecutive passes. The pattern is designed as necessary to ablate tissue, but minimize the undesired accumulation of heat in nearby tissue. Preferably, utilization of a beam pattern as described reduces sensations of pain, and also reduces injury of non-targeted tissue. In some of these embodiments, the tissue is actively cooled, preceding and/or following application of the energy thereto.
In some preferred embodiments of the present invention, a cover is placed over the target area, and the electromagnetic energy is applied through a window in the cover. Preferably, the cover enables an operator to maintain an ambient environment over the target area having properties, such as temperature, pressure, and humidity, which are set so as to minimize pain or discomfort during a procedure. Typically, sensors are coupled to the cover in order to determine parameters of the ambient environment and to generate signals responsive thereto. A control unit is preferably coupled to receive the signals and to actuate various devices so as to cause the signals to converge to desired values. The devices may include, for example, heating and cooling elements, pressure and humidity controllers, and a substance-delivery system. In a preferred embodiment, a temperature sensor monitors skin temperature, and active heating (e.g., using a laser) and cooling are applied as appropriate to keep the skin temperature within predetermined limits.
In a preferred embodiment of the present invention, the target area comprises two or more zones, typically concentrically-arranged, and the electromagnetic energy source applies a different amount of energy to one of the zones from the amount applied to a second one of the zones. Preferably, the highest quantity of energy is applied to the innermost of the concentric zones, and successively smaller quantities of energy are applied to the other zones, responsive to their distance from the innermost zone. In this manner, a smooth transition is obtained from the target area to tissue or material surrounding the target area. By contrast, it is known in the art to use chemical or laser treatments for cosmetic purposes, such as wrinkle removal, but these treatments are typically disadvantageous, in that they often leave a region which clearly appears to have been treated, adjacent to a second region, which clearly has not been treated. For example, when these prior art methods are practiced to achieve wrinkle removal in the mustache area, a patch of generally wrinkle-free skin may be produced, but the patch is often sharply delineated from its neighboring, still-wrinkled skin.
In another preferred embodiment of the present invention, the target area comprises skin, and application of the energy thereto causes pores in the skin to expand. Pore expansion may be used to enhance transdermal drug delivery and/or as part of an acne treatment. Alternatively, drug delivery and acne treatment are performed responsive to the skin""s ablation, irrespective of any pore expansion that may occur.
In some preferred embodiments of the present invention, a high absorption substance (HAS) is applied to the target area prior to activation of the electromagnetic energy source, so as to increase the absorption of energy in the target area.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for applying energy to biological tissue, including:
directing an electromagnetic energy source to apply the energy to a region of the tissue, so as to ablate a portion of the tissue in the region; and
initiating cooling of tissue in the region subsequent to the ablation.
In a preferred embodiment, initiating cooling includes thermoelectrically cooling.
In a preferred embodiment, the method includes applying to the tissue gaseous oxygen at a concentration above 22% by volume to enhance healing of the tissue. Alternatively or additionally, an oxygen-rich solution is applied to the tissue to enhance healing of the tissue. Further alternatively or additionally, a nutrient is applied to the tissue.
Preferably, directing the energy source to apply the energy includes generating a beam of energy having a diameter less than about 250 microns. Further preferably, directing the energy source to apply the energy includes generating a beam of energy having a dwell time over a point in the region of less than 25 ms.
In a preferred embodiment, the tissue includes a varix. Alternatively, the tissue includes tumorous tissue.
In a preferred embodiment, initiating cooling includes applying a cooled surface to the tissue. Preferably, applying the cooled surface includes applying a cooled oscillating member to the tissue, which member is in contact with the tissue during a first phase of its oscillation and is not in contact with the tissue during a second phase of its oscillation.
Preferably, initiating cooling includes applying a coolant. Further preferably, the coolant includes a liquid and the method includes directing a flow of a gas towards a site on the tissue having the liquid applied thereto, so as to increase a rate of evaporation of the liquid.
In a preferred embodiment, the region includes a first region, and initiating cooling includes initiating cooling of tissue in the first region, wherein the method includes terminating cooling of the tissue in the first region subsequent to initiating the cooling thereof, and wherein the method includes directing the source to apply energy to a second region of the tissue so as to ablate a portion of the tissue in the second region subsequent to the initiation of cooling of the tissue in the first region. Alternatively or additionally, directing the source to apply the energy to the second region includes directing the source prior to the termination of the cooling of the tissue in the first region.
In a preferred embodiment, the region includes a first region, and ablating the portion includes ablating tissue to a first ablation depth in the first region. In this embodiment, the method includes directing the electromagnetic energy source to apply energy to a second region of the tissue adjacent to the first region, so as to ablate tissue in the second region to a second ablation depth, smaller than the first ablation depth. Typically, directing the source to apply energy to the second region includes smoothing the appearance of a border region between the first region and an untreated region of the tissue.
Preferably, the tissue includes skin, and the energy is applied so as to reduce a wrinkle in the skin and/or to decrease the size of a skin lesion. Alternatively or additionally, applying the energy includes expanding a pore of the skin, and, optionally, delivering a pharmaceutical product through the expanded pore.
In a preferred embodiment, the method includes applying a pharmaceutical product to the tissue. Typically, applying the product includes applying an anesthetic and/or an antibiotic.
Preferably, applying the energy to the region of the tissue includes placing a material on the tissue to increase the absorption into the tissue of energy applied by the source. Further preferably, the material includes a substance characterized by high absorbency of energy of a wavelength generated by the source. Still further preferably, the energy source includes a CO2 laser. Alternatively or additionally, the output of the energy source is less than about 5 W.
In a preferred embodiment, the electromagnetic energy source includes a broadband emission lamp. Alternatively or additionally, the electromagnetic energy source includes a laser, typically a CO2 laser, an Er:YAG laser, a microchip laser, and/or a diode laser. Preferably, the diode laser has a power output of less than about 500 mW.
Preferably, the method includes actively warming tissue cooled responsive to the cooling, so as to decrease injury of the cooled tissue. Typically, warming includes sensing a temperature of the tissue and warming the tissue responsive thereto. In a preferred embodiment, warming includes applying a heated gas to the tissue. Alternatively or additionally, warming the tissue includes thermoelectrically warming the tissue, and initiating cooling includes thermoelectrically cooling the tissue. Further alternatively or additionally, warming includes applying a heated surface to the tissue. In a preferred embodiment, warming the tissue includes directing the energy source to apply additional energy to the cooled tissue, which additional energy substantially does not cause ablation. Typically, applying the additional energy includes enlarging a beam diameter of the energy source from a first diameter, used for ablating tissue, to a second diameter, used for warming tissue.
There is further provided, in accordance with a preferred embodiment of the present invention, a method for applying energy to biological tissue, including:
directin an electromagnetic energy source to apply energy along a first path on the tissue, so as to ablate tissue in the path;
directing the source to apply energy along a second path on the tissue, relatively distant from the first path, so as to ablate tissue in the second path, while allowing cooling of tissue adjacent to the first path heated by diffusion due to applying the energy to the first path; and
directing the source to apply energy along a third path on the tissue, closer to the first path than to the second path, so as to ablate tissue therein.
Preferably, applying the energy along the first path includes placing a material on the tissue to increase the absorption into the tissue of energy applied by the source. Further preferably, the material includes a substance characterized by high absorbency of energy of a wavelength generated by the source.
In a preferred embodiment, the method includes actively cooling tissue in a vicinity of the first path. Preferably, actively cooling includes initiating the active cooling subsequent to ablation of the tissue in the first path. Alternatively or additionally, actively cooling includes applying a coolant in the vicinity of the first path. Further alternatively or additionally, actively cooling includes thermoelectrically cooling. Still further alternatively or additionally, actively cooling includes applying a cooled surface to the tissue in the vicinity of the first path. Typically, applying the cooled surface includes applying a cooled oscillating member to the tissue in the vicinity of the first path, which member is substantially not in contact with the tissue in the vicinity of the first path during a first phase of its oscillation and is in contact with the tissue in the vicinity of the first path during a second phase of its oscillation. Directing the electromagnetic energy source to apply energy along the first path on the tissue generally includes directing the source during the first phase.
In a preferred embodiment, the method includes applying a pharmaceutical product in a vicinity of the first path.
There is still further provided, in accordance with a preferred embodiment of the present invention, a method for applying energy to biological tissue, including:
placing a cover on the tissue; and
directing a beam of electromagnetic energy through the cover to impinge on the tissue, so as to ablate a portion thereof.
Preferably, the cover includes a window, through which the energy beam passes.
Further preferably, placing the cover on the tissue reduces stimulation of nerves therein. Typically, placement of the cover defines a volume of an intermediate substance, between the cover and the tissue, and reducing stimulation includes maintaining a desired characteristic of the intermediate substance. The substance may include air and/or a liquid. In a preferred embodiment, the characteristic includes a temperature, a pressure, and/or humidity.
There is yet further provided, in accordance with a preferred embodiment of the present invention, a method for applying energy to biological tissue of a subject, including:
directing an electromagnetic energy source to apply the energy to a region of the tissue, so as to ablate a portion of the tissue in the region;
applying a liquid coolant to the tissue; and
directing a flow of a gas towards the tissue, so as to increase a rate of evaporation of the liquid coolant.
Typically, the gas is directed to the tissue so as to reduce a perception of discomfort by the subject responsive to the coolant.
There is also provided, in accordance with a preferred embodiment of the present invention, apparatus for applying energy to biological tissue, including:
an electromagnetic energy source, directed to apply the energy to a region of the tissue, so as to ablate a portion of the tissue in the region; and
a cooling unit, which initiates cooling of tissue in the region subsequent to the ablation.
In a preferred embodiment, the cooling unit includes a thermoelectric cooling unit.
Alternatively or additionally, the apparatus includes a pharmaceutical delivery unit, containing a pharmaceutical product for application to the tissue in a vicinity of the ablated portion.
Further alternatively or additionally, the apparatus includes a heating unit, which heats tissue cooled by the cooling unit, so as to decrease injury of the cooled tissue. Preferably, the apparatus includes a temperature sensor, which generates a signal responsive to a temperature of the tissue, wherein the heating unit heats the tissue responsive to the signal. In a preferred embodiment, the heating unit includes a thermoelectric element, through which element current is driven in a first direction so as to heat the tissue. Preferably, the cooling unit drives current through the thermoelectric element in a second direction so as to cool the tissue. Alternatively or additionally, the heating unit includes a heated surface which is applied to the tissue.
There is additionally provided, in accordance with a preferred embodiment of the present invention, apparatus for applying energy to biological tissue, including:
an electromagnetic energy source, which applies energy to the tissue; and
a beam scanner, which directs the energy from the source along a plurality of paths on the tissue, including (a) a first path, so as to ablate tissue in the first path, (b) a second path, relatively distant from the first path, so as to ablate tissue in the second path, while allowing cooling of tissue adjacent to the first path heated by diffusion due to applying the energy to the first path, and (c) a third path, closer to the first path than to the second path, so as to ablate tissue in the third path.
There is yet additionally provided, in accordance with a preferred embodiment of the present invention, apparatus for applying energy to biological tissue, including:
a cover, placed on the tissue; and
an electromagnetic energy source, which directs a beam of energy through the cover to impinge on the tissue, so as to ablate a portion thereof.
Preferably, the apparatus includes a pharmaceutical reservoir, containing a pharmaceutical product for application to the tissue.
There is also provided, in accordance with a preferred embodiment of the present invention, apparatus for applying energy to biological tissue of a subject, including:
an electromagnetic energy source, directed to apply the energy to a region of the tissue, so as to ablate a portion of the tissue in the region; and
a cooling unit, which applies a liquid coolant to the tissue and directs a flow of a gas towards the tissue, so as to increase a rate of evaporation of the liquid coolant.
preferably, the cooling unit directs the gas to the tissue so as to reduce a perception of discomfort by the subject responsive to the coolant.